Problem: $ { \left[\begin{array}{rrr}{-1} & {0} & {-2} \\ {0} & {1} & {-1}\end{array}\right]+\left[\begin{array}{rrr}{-1} & {3} & {3} \\ {0} & {1} & {4}\end{array}\right] = {?} } $
Solution: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rrr}{-1}+{-1} & {0}+{3} & {-2}+{3} \\ {0}+{0} & {1}+{1} & {-1}+{4}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{-2} & {3} & {1} \\ {0} & {2} & {3}\end{array}\right]}$